Post date refers to the writing of a future date on a check. For example, someone writes a check that is dated March 31, even though the current date is March 15. The intent behind this dating arrangement is to force the payee to wait until the post date arrives before cashing the check. There are two reasons for doing so:

The payer does not currently have sufficient cash in his checking account, and so sets a future date in the expectation of adding more cash to his checking account that will then be used to fund the check.

The payer cannot be bothered with a series of check payments to the payee, and instead issues all of the checks at once, with each check post dated to a successively later date. For example, a tenant could write 12 checks to his landlord at the beginning of the lease year, with each one dated to cover the check payment for each successive month of the year. The landlord is then instructed to cash the checks as they come due.